Continuous wave optical parametric oscillator for quartz-enhanced photoacoustic trace gas sensing

A continuous wave optical parametric oscillator, generating up to 300 mW idler output in the 3–4 μm wavelength region, and pumped by a fiber-amplified DBR diode laser is used for trace gas detection by means of quartz-enhanced photoacoustic spectroscopy (QEPAS). Mode-hop-free tuning of the OPO output over 5.2 cm-1 and continuous spectral coverage exceeding 16.5 cm-1 were achieved via electronic pump source tuning alone. Online monitoring of the idler wavelength, with feedback to the DBR diode laser, provided an automated closed-loop control allowing arbitrary idler wavelength selection within the pump tuning range and locking of the idler wavelength with a stability of 1.7×10-3 cm-1 over at least 30 min.\ud \ud Using this approach, we locked the idler wavelength at an ethane absorption peak and obtained QEPAS data to verify the linear response of the QEPAS signal at different ethane concentrations (100 ppbv-20 ppmv) and different power levels. The detection limit for ethane was determined to be 13 ppbv (20 s averaging), corresponding to a normalized noise equivalent absorption coefficient of 4.4×10-7 cm-1  W/Hz1/2

Small-Size Resonant Photoacoustic Cell of Inclined Geometry for Gas Detection

A photoacoustic cell intended for laser detection of trace gases is represented. The cell is adapted so as to enhance the gas-detection performance and, simultaneously, to reduce the cell size. The cell design provides an efficient cancellation of the window background (a parasite response due to absorption of laser beam in the cell windows) and acoustic isolation from the environment for an acoustic resonance of the cell. The useful photoacoustic response from a detected gas, window background and noise are analyzed in demonstration experiments as functions of the modulation frequency for a prototype cell with the internal volume ~ 0.5 cm^3. The minimal detectable absorption for the prototype is estimated to be ~ 1.2 10^{-8} cm^{-1} W Hz^{-1/2}.Comment: 11 pages, 5 figure

Методы, процедуры и инструменты диверсификации предприятий и организаций ОПК России

Purpose: the work covers the issues of organizational, methodological and instrumental support of the processes of diversification of organizations and enterprises of the Russian defense industry complex. Based on an analysis of the reasons for the low efficiency of federal targeted programs for the conversion of enterprises and the organization of the military-industrial complex in 1993-1997, proposals for its improvement were formulated.Methods: the methodological basis of the approach considered in the article is to assess the effectiveness of diversification, including both parameters of the use of production capacity and the main results of the production activities of economic entities.Results: the article proposed and justified: 1) the principles of diversification of enterprises and defense industry organizations; 2) tools for assessing the economic consequences, based on justifying calculations of the use of production capacity, determining the need for resources, the volume of capital investments and production areas; 3) action plan (“roadmap”) for the development and production of high-tech civilian products.Conclusions and Relevance: Diversification of enterprises and organizations of the defense-industrial complex of the Russian Federation in most cases (except for dual-use products) requires an investment of a considerable amount of funds. In order to ensure the minimization of the resources required for its fulfillment (amount of capital investments, production space and labor force), the use of the production potential load factor is proposed as a criterion for evaluation of conversion efficiency of military production. Цель: В работе освещаются вопросы организационно-методического и инструментального обеспечения процессов диверсификации организаций и предприятий российского оборонно-промышленного комплекса. На основе анализа причин низкой эффективности федеральных целевых программ конверсии предприятий и организации ВПК в 1993–1997 гг. были сформулированы предложения по ее повышению.Методология проведения работы: Методической основой рассматриваемого в статье подхода является оценка эффективности диверсификации, включающую как параметры использовании производственных мощностей, так и основные результаты производственной деятельности хозяйствующих субъектов.Результаты работы: В статье предложены и обоснованы: 1) принципы диверсификации предприятий и организаций ОПК; 2) инструментарий оценки экономических последствий, основанный на обосновывающих расчетах использования производственных мощностей, определении потребности в ресурсах, объемах капитальных вложений и производственных площадях; 3) план мероприятий («дорожная карта») проведения работ по освоению и производству высокотехнологичной гражданской продукции.Выводы: Диверсификация предприятий и организаций ОПК Российской Федерации требует в большинстве случаев (кроме продукции двойного назначения) вложения значительной суммы средств. С целью обеспечения минимизации требуемых для ее выполнения ресурсов (объемов капитальных вложений, производственных площадей и рабочей силы) в качестве критерия оценки эффективности конверсии военного производства, предлагается использование коэффициента загрузки производственного потенциала.

Load Monitoring CEC/LMTF Load Research Program

This white paper addresses the needs, options, current practices of load monitoring. Recommendations on load monitoring applications and future directions are also presented

Cavity-enhanced direct frequency comb spectroscopy

Cavity-enhanced direct frequency comb spectroscopy combines broad spectral bandwidth, high spectral resolution, precise frequency calibration, and ultrahigh detection sensitivity, all in one experimental platform based on an optical frequency comb interacting with a high-finesse optical cavity. Precise control of the optical frequency comb allows highly efficient, coherent coupling of individual comb components with corresponding resonant modes of the high-finesse cavity. The long cavity lifetime dramatically enhances the effective interaction between the light field and intracavity matter, increasing the sensitivity for measurement of optical losses by a factor that is on the order of the cavity finesse. The use of low-dispersion mirrors permits almost the entire spectral bandwidth of the frequency comb to be employed for detection, covering a range of ~10% of the actual optical frequency. The light transmitted from the cavity is spectrally resolved to provide a multitude of detection channels with spectral resolutions ranging from a several gigahertz to hundreds of kilohertz. In this review we will discuss the principle of cavity-enhanced direct frequency comb spectroscopy and the various implementations of such systems. In particular, we discuss several types of UV, optical, and IR frequency comb sources and optical cavity designs that can be used for specific spectroscopic applications. We present several cavity-comb coupling methods to take advantage of the broad spectral bandwidth and narrow spectral components of a frequency comb. Finally, we present a series of experimental measurements on trace gas detections, human breath analysis, and characterization of cold molecular beams.Comment: 36 pages, 27 figure

Laser spectroscopy for breath analysis : towards clinical implementation

Detection and analysis of volatile compounds in exhaled breath represents an attractive tool for monitoring the metabolic status of a patient and disease diagnosis, since it is non-invasive and fast. Numerous studies have already demonstrated the benefit of breath analysis in clinical settings/applications and encouraged multidisciplinary research to reveal new insights regarding the origins, pathways, and pathophysiological roles of breath components. Many breath analysis methods are currently available to help explore these directions, ranging from mass spectrometry to laser-based spectroscopy and sensor arrays. This review presents an update of the current status of optical methods, using near and mid-infrared sources, for clinical breath gas analysis over the last decade and describes recent technological developments and their applications. The review includes: tunable diode laser absorption spectroscopy, cavity ring-down spectroscopy, integrated cavity output spectroscopy, cavity-enhanced absorption spectroscopy, photoacoustic spectroscopy, quartz-enhanced photoacoustic spectroscopy, and optical frequency comb spectroscopy. A SWOT analysis (strengths, weaknesses, opportunities, and threats) is presented that describes the laser-based techniques within the clinical framework of breath research and their appealing features for clinical use.Peer reviewe